I never really noticed the rivet between the Tin Man’s eyes before. Or the delicately applied flakes of rust on his face.

Nor had I noticed the rough threading, drawn by hand, on the “burlap” that enveloped the lower half of the Scarecrow’s face.

These are two of the small pleasures to be gleaned from the 75th anniversary edition of “The Wizard Oz,” released last year by Warner Home Video. The star of this two-disc set is, of course, the movie itself, which a team of visual and sound experts restored digitally, a painstaking process that consumed hundreds of work hours.

The three-strip Technicolor images look better than they did in movie theaters in 1939, according to the restoration specialists interviewed for one of the “extras” on the DVD.

Audio engineers converted the original mono soundtrack to 5.1 stereo, giving the film enhanced music and sound-effects tracks, although using only the original elements. The disc gives you the option of listening to the original mono soundtrack if you want to compare.

You can find different versions of the 75th anniversary edition, including one in 3-D on Blu-ray, but this relatively simple two-disc set met my purposes.

Among the extras are bios of the principals (including Toto), a documentary on the making of the film that includes information on the casting choices and how MGM’s parent company, Loewe’s Inc., bridled at the film’s snowballing budget. Shirley Temple was considered for Dorothy, but her singing ability was too limited, and W.C. Fields was apparently in contention to play the Wizard before the role went to Frank Morgan.

The extras include home movies from the set shot by songwriter Harold Arlen, notably the elaborate “Jitterbug” number that was cut from the film, and recordings of unused musical numbers, including “If I Only Had a Heart” by Buddy Ebsen, the original Tin Man.

You can also watch the film with a commentary track recorded when many of the important contributors were still alive. Among them were Margaret Hamilton (the Wicked Witch), Ray Bolger (the Scarecrow), Jack Haley (who inherited the role of the Tin Man after Ebsen became ill inhaling the aluminum-powder makeup), Ebsen and producer Mervyn LeRoy.

The package includes test footage of the tornado, shot on a soundstage with a miniature farmhouse. The twister was an inventive gizmo that consisted of a silk stocking stretched over chicken wire designed to move back and forth along the “prairie”; combined with the voluminous clouds of dust from the tech crews, the effect is truly scary.

The shots of Dorothy and Aunt Em with the tornado in the background were shot with the actors and minimal set pieces in front of a rear-screen projection.

Even the casual viewer can pick up a wealth of technical information about the making of “Oz,” all of it pretty impressive.

Many of the long shots were combinations of live footage and matte painting, for example; the process wasn’t new, but it had never been used so impressively. For comparison, take a look at “Gone With the Wind,” released the same year, in which certain shots were never finished because the technicians and artists ran out of time.

According to the documentary, MGM also pioneered the art of lip syncing. Music and vocal tracks were recorded in advance, and on set the actors mouthed the lyrics to a playback recording as they performed. It allowed numerous moving shots, which was no small thing with Technicolor cameras the size of a refrigerator.

Some of the more dubious extras include a too-long piece on the film’s “legacy,” focusing on Oz festivals with guest appearances by former Munchkins, and a short promotional film on the importance of Hoover Dam to the film industry.

In separate features, we learn that MGM had its own power plant and that the elaborate indoor “Oz” sets required so much light to shoot in Technicolor that Culver City, Calif., experienced brown-outs. The soundstage doors were opened each time shooting stopped so cast and crew could get away from the stifling heat for a few minutes.

Also on hand to comment on the film’s still-impressive artistry are composer Randy Newman, makeup artist Rick Baker and film director/choreographer Rob Marshall, among others.

All the background information is nice, some of it fascinating, but at the end of the day what remains is the film itself. By rights, a masterpiece should never have been possible with mid-production cast changes, costume redesigns, five directors and as many as 15 writers. But that’s what the film is.

Some of those interviewed, including Marshall, argue that “Oz” is the greatest American film. It had plenty of competition for that honor in 1939, including “Gone With the Wind” and John Ford’s “Stagecoach,” but after watching the movie again in a visually perfect digital restoration, I can’t disagree.

The Wizard of August

We’re celebrating this month’s 75th anniversary of “The Wizard of Oz” movie with a story a day.

Friday in FYI: The winners of our Oz photo caption contest.

‘Oz’ on video

The Warner Home Video 2013 release of the restored 75th anniversary edition of “The Wizard of Oz” is available in DVD and Blu-ray with various levels of goodies included. The film is available from Amazon, Barnes & Noble and other outlets.